question about running anti spam in multiple ZCS server environment

Hello,

Our ZCS installation runs on two servers. One of them is the main MTA and runs all of the services, including antispam, and has a handful of mailboxes on it. The second one is home to the majority of our mailboxes, and mailbox and spell checker are the only services running on it. I have noticed that users whose mail boxes are on our second server, are not getting their junk mail processed correctly. I mean, most of the junk mail is properly filtered into the junk folder, but once they are there, they are not being held to the rules for junk mail, such as the max age, so they are not being deleted. I also think they are not being used to train the filter. Does anyone know how I can activate the anti spam on our second server? We are using Realase 5.0.2_GA_1976.RHEL4_20080130204528 CentOS4 NETWORK edition.